Effect of hyperoxia on surfactant protein gene expression in hypoplastic: lung in nitrofen-induced diaphragmatic hernia in rats

The hypoplastic lung in congenital diaphragmatic hernia (CDH) has both a qu antitative and qualitative reduction in surfactant. Recently, the role of o xygen (O-2) as a. regulator of pulmonary surfactant-associated protein (SP) gene expression has been reported. The mRNA level of SP has been demonstra ted to be increased in the lungs of animals exposed to hyperoxia. The aim o f this study was to investigate SP mRNA expression in hypoplastic CDH lung in rats during mechanical ventilation in order to determine the effect of O -2 on SP synthesis in CDH. A CDH model was induced in pregnant rats followi ng administration of nitrofen. The newborn rats with CDH and controls were intubated and ventilated. Ventilation was continued for 6 h under 100% oxyg en. Reverse-transcription polymerase chain reaction (RT-PCR) was performed to evaluate the relative amounts of mRNA expression of SP-A, SP-B, SP-C, an d SP-D. Relative amounts of SP-A, SP-B, and SP-D mRNA expression in CDH lun g were significantly decreased compared to controls at birth and 6 h after ventilation. There was no significant difference in SP-C mRNA expression be tween CDH animals and controls. Upregulated mRNA expression of SP-A, SP-B, and SP-D in lungs of control animals at 6 h after ventilation suggests that oxygenation accelerates postnatal SP synthesis in normal lungs. The inabil ity of O-2 to increase SP mRNA expression in hypoplastic CDH lung suggests that the hypoplastic lung is not responsive to increased oxygenation for th e synthesis of SP.